(1) Field of the Invention
The present invention relates to a paste composition and a printed circuit board using the same.
(2) Description of Related Art
In recent years, clean energies, which hardly cause harmful substances to be generated in use, have been paid attention to, and cells using the clean energies, e.g., fuel cells and solar cells have been developed. Particularly, small-sized and high-capacity cells are required for mobile devices such as mobile phones. Therefore, fuel cells capable of obtaining higher energy densities than those in conventional cells such as lithium secondary cells have been paid attention to. The fuel cells include direct methanol fuel cells.
In the direct methanol fuel cell, methanol is decomposed with a catalyst, to form hydrogen ions. The hydrogen ions and oxygen in air are reacted with each other, to generate electric power. In this case, chemical energy can be significantly efficiently converted into electric energy so that a very high energy density can be obtained.
A flexible printed circuit board (hereinafter abbreviated as an FPC board) is provided as a collection circuit inside the direct methanol fuel cell (see, e.g., JP 2004-200064 A).
The FPC board has a configuration in which a conductor layer is formed on a base insulating layer having flexibility. A part of the FPC board is pulled out of a fuel cell. Various external circuits are connected to a portion, which has been pulled out of the fuel cell, of the FPC board.
When methanol supplied as fuel to the direct methanol fuel cell reacts with oxygen, formic acid having a strong corrosive action is produced. The formic acid causes a conductor layer in the FPC board to corrode.